Re: TR4310 HF Transceiver
On trying to use a Drake SP75 Speech Processor with the TR4310 Communications Transceiver.
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I'm pleased to report that the TR4310 has been working flawlessly since it's recent major surgery. I have been using it on 160, 80 and 40 with a Shure 444 microphone, which I find always produces great results with any TX or TRx from the same era. I've replaced the Drake FA-7 110 Volt AC cooling fan with a 12 Volt DC computer-type one - about 5 Volt DC gets it spinning nicely without screaming. I don't like the US practice of routing AC primary mains into radios for on/off switching, or fans, especially where the radio is otherwise fully low-voltage DC powered.
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The job lot of Drake I bought some while ago included an SP75 Speech Processor. The SP75 is a proper RF Clipper, with a compression stage on the front. I'm a big fan of the Datong 'ASP' Automatic RF Speech Processor units, made in the UK many years ago. The SP75 uses the filter method (at 459 kHz) to create it's SSB, while the Datong uses the phasing method. I thought the SP75 would make a nice companion for my TR7 / TR4310 and free-up a Datong for use with other vintage radio here.
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On plugging the Drake processor into the TR4310, it behaved rather strangely. The 'on' LED would only illuminate when the microphone PTT was pressed. It passed audio when it did that sounded not too bad. When the case of the processor touched the case of the transceiver, the transceiver went into transmit!?!
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I pulled the processor apart and checked it's jumper settings, microphone socket and microphone plug wiring against the schematic. All in agreement.
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Next I put the manuals for the TR7 and TR4310 side by side. Surely Drake would not wire the microphone sockets differently between amateur and commercial versions of, largely, the same product, would they. The cynic in me thought they just might, in order to add a barrier to commercial users trying to cheap-out and use accessories from the amateur line. No! I banished my cynical thoughts - the wiring was specified as identical.
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That left only one possible cause: The wiring of the microphone socket in the TR4310 was wrong / not as designed. I flipped the TR4310 over and put it side-by-side with the flipped-over TR7 that had been supporting it all these weeks. The microphone socket in the '4310 was mirror image vertically of that in the TR7. So, what should have been ground on the connector was wired as PTT and vice versa. What should have been hi-level mic audio was wired as lo-level and vice versa. The soldering did not look too bad, but less good than I would have expected ex-factory. I re-wired it to be correct against the schematic and concluded that the wiring error was introduced when someone had the front panel off previously. I can see that the movable photo interrupter, part of the tuning dial, has been changed. If the fixed one has been changed too, that would have necessitated front-panel removal.
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Now to try the processor to see how it performs!
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Regards,
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Mark, G4FPH.
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Re: AC-4 Power Supply 10K Bias Trimmer Replacement
Hi Joe,
Try oldradioparts.net. Mark Oppat stocks literally thousands of potentiometers in every possible configuration, and will even customize them for you if needed. Very reasonable prices for unobtainium parts.
73, Graham N6GH
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On Feb 3, 2025, at 3:17?PM, Joe W7BWA via groups.io <W7BWA@...> wrote:
? I purchased an AC-4 power supply and noticed one of the 3 lugs was snapped off.
Lots of 10Ks out there, but not with two mounting fins for the case.
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Has anyone replaced these and found a suitable replacement?
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Many thanks! 73.
--
Joe - W7BWA
Custer, WA
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Mostly agreed but has nothing to do with distortion. Passive microphones, which include crystal, ceramic, magnetic, moving coil, ribbon are generators. They look like voltage sources. They do have a characteristic electrical impedance, which is stated in their specs, but they are voltage sources, as the OP states, not power sources. Non generator microphones, which include condenser and carbon microphes, are not generators. Carbon microphones are "valves" where the carbon acts as a variable resistance. There is a current source which is varied by the microphone resistance, which in turn, depends on the pressure on the resistive element by the diaphragm. Carbon microphones have the property of being amplifiers and for that reason were almost universally used in telephone systems where power is important. A condenser microphone is a variable condenser. It is used to either vary a voltage charge put on it by a voltage supply, or to vary the frequency of an oscillator. Condenser microphones always need some sort of electronic amplfier, or rather an impedance matcher or else a combination oscillator/detector.
An electret microphone is a condenser microphone with a permanent charge. It is the condenser equivalent of a permanent magnet. Electret microphones, like condenser mics, need an amplifier or impedance matcher. They are very simple and can be made with very high fidelity. Electret mics require very little power and have supplanted condenser mics for many purposes and carbon mics for almost all purposes.
The required load impedance for generator microphones (crstal, dynamic) is, essentially infinite, since they are voltage sources. In some cases the load impedance will affect the frequency response. This is the case for ribbon and directional moving coil mics where _matching_ the impedance will cause a loss of low frequency response as well as an overall loss of level. The British (BBC) actually prefer to load microphones. Where the frequency response is of interest the microphone is built with internal damping and equalization. I have had some arguments with British sound engineers over the virtues of loading. They are wrong about this. BTW, Western Electric did much the same thing their speech imput amplifiers mainly to avoid expensive input transformers.
Condenser and electret mics are essentially electronic so the source impedance is an electronic circuit and can be made whatever is desirable for the application. Many European condenser mics require a given load impedance to eliminate resonances in the transformers. But, because the signal to noise ratio is determined by the amplifier and not the microphone element, the levels vs load impedance is of no consequence.
At some point
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On 2/3/2025 6:26 PM, jerry-KF6VB wrote: On 2025-02-03 17:12, Jim Shorney via groups.io wrote:
Impedance matching
in microphone circuits is a myth. *** Agree 100%.? Microphones are about VOLTAGE, not power.? Want low
distortion?? Don't load it down!
?????????????? - Jerry, KF6VB
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Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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On 2025-02-03 17:12, Jim Shorney via groups.io wrote: Impedance matching in microphone circuits is a myth. *** Agree 100%. Microphones are about VOLTAGE, not power. Want low distortion? Don't load it down! - Jerry, KF6VB
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Re: The mysteriously modified 7077 (and nothing else¡)
Point taken. I haven¡¯t spent much on radio lately, so I owe it to myself :-D
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 20:47, Jim Shorney via groups.io < jimNU0C@...> wrote:
I hate to say it but you might be better off with the Heil cartridge. In my mic comparison runs, the 7077 cam in dead last behind various vintage Shure, Turner, E-V, and modified D-104/UGxx microphones for audio quality.
On Tue, 04 Feb 2025 01:36:40 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> If I have to, I can install a Heil kit and know that I will have a good mic. But if I can regain the performance without spending another $70, I¡¯m good with that.
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73
-Jim
NU0C
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Re: The mysteriously modified 7077 (and nothing else¡)
I hate to say it but you might be better off with the Heil cartridge. In my mic comparison runs, the 7077 cam in dead last behind various vintage Shure, Turner, E-V, and modified D-104/UGxx microphones for audio quality. On Tue, 04 Feb 2025 01:36:40 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: If I have to, I can install a Heil kit and know that I will have a good mic. But if I can regain the performance without spending another $70, I¡¯m good with that. -- 73 -Jim NU0C
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Re: The mysteriously modified 7077 (and nothing else¡)
Yeah, they did the second time.?
It¡¯s frustrating.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 20:35, Joe - W7RKN via groups.io < w7rkn.7@...> wrote:
Teve¡none of your images cam through!
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Joe ¨C W7RKN
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From: [email protected] [mailto:[email protected]] On Behalf Of Steve Wedge, W1ES/4 via groups.io
Subject: [DRAKE-RADIO] The mysteriously modified 7077 (and nothing else¡)
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Here are some pics of what I found inside.?
I have doubts as to the originality of the element itself, as it measures 430 ohms, resistive.?
First photo shows what the element looks like in its housing. This all came apart without any tools.?
This is what the element looks like.?
This is the kludge I found in the base.?
Time flies like an arrow. Fruit flies like a banana.
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"Normal" is the one shown in my photos. On Tue, 04 Feb 2025 01:31:29 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: I¡¯d just like to put the thing back to original.
Even the Heil elements now have transformers.
Steve Wedge, W1ES
-- 73 -Jim NU0C
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Re: The mysteriously modified 7077 (and nothing else¡)
It was working fine until Sunday. Perhaps, I¡¯ll try resoldering all the bad-looking connections and/or testing the transformer. As bad as it looks, it was working.?
Most of the stuff I see on eBay looks like ¡°pig-in-a-poke¡±stuff. If I have to, I can install a Heil kit and know that I will have a good mic. But if I can regain the performance without spending another $70, I¡¯m good with that.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 20:16, Jim Shorney via groups.io < jimNU0C@...> wrote:
That seems likely to be the same cartridge shown in the photos I posted to the group photos section. And yes, as I mentioned previously, it is a cheap CB-era low impedance dynamic cartridge. Thus the need for the transformer to step up the voltage.
On Mon, 03 Feb 2025 21:09:56 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> I have just about run to the end of my patience with apps and webpages that still think they¡¯re in 1993.
>
> I should be able to up load photos. I will try again.
>
> Steve Wedge, W1ES
>
--
73
-Jim
NU0C
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Re: The mysteriously modified 7077 (and nothing else¡)
Teve¡none of your images cam through! ? Joe ¨C W7RKN ? From: [email protected] [mailto:[email protected]] On Behalf Of Steve Wedge, W1ES/4 via groups.io
Subject: [DRAKE-RADIO] The mysteriously modified 7077 (and nothing else¡) ? Here are some pics of what I found inside.? I have doubts as to the originality of the element itself, as it measures 430 ohms, resistive.? First photo shows what the element looks like in its housing. This all came apart without any tools.?
This is what the element looks like.?
This is the kludge I found in the base.?
Time flies like an arrow. Fruit flies like a banana.
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Re: Drake TR7, TX issue any ideas?
This is shown on the schematic. It appears you may have an early board. The PIN diodes are different also. This pair of PINs are used to inject the calibrator signal. On Mon, 03 Feb 2025 10:57:20 -0800 "Michael Jensen via groups.io" <kavigal@...> wrote: On further inspection I found this:
Those 2 pin diodes connected to a cap? It looks like some modification, how ever I see no holes in the PCB where those 2 pin diodes would go otherwise.
Early version of this board and legit or? -- 73 -Jim NU0C
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I¡¯d just like to put the thing back to original.?
Even the Heil elements now have transformers.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 20:12, Jim Shorney via groups.io < jimNU0C@...> wrote:
That's what the transformer is for. Although I will say it again, it is not impedance matching. It is a voltage step-up. Impedance matching in microphone circuits is a myth. This is well documented on the internet. Impedance matching is only important when you are transferring power. In fact the pro audio world recommends that the load impedance be 10x the microphone impedance.
https://www.prosoundtraining.com/2010/11/03/microphone-mythbusters-vol-5-impedance-matching/
On Mon, 03 Feb 2025 16:47:04 +0000
"Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote:
> One thing of note that I will repeat here is that the element itself -- disconnected from the rest of the mic -- measures 430 ohms with my Fluke 77 in resistance mode. That seems odd if the thing is supposed to be high-impedance.
--
73
-Jim
NU0C
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I prefer the C in tight quarters on CW. You can get crystal filters down to 250 Hz stock and 125 Hz if you search. In pileups, these are the equal to newer rigs¡¯ receivers.?
For everyday, casual CW, the B sounds quite nice.?
Understand that the shape factors of the two rigs¡¯ filters are fairly different. Some prefer one over the other.?
The CW subbands aren¡¯t as crowded as they were 20 years ago, so take that into consideration.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 15:17, Craig W8CS via groups.io < craig_severson@...> wrote:
Hi Scott, have you read the VE3EFJ "Drakemod" manifesto? If I recall Wayne's verbiage, it's something like this:
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The R-4B is a terrific receiver out of the box and it does everything well, however you won't get the selectivity of an R-4C. The R-4C stock is a bit of a waste compared to its potential due to some questionable design choices. A properly (Sherwood) modified R-4C is transformed and is an exceptional receiver.?
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Others will have a much more technical take than mine. The 4B is great out of the box; the 4C requires some work to realize exceptional potential.?
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Craig/W8CS
Greenville, SC
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Re: Drake TR7, TX issue any ideas?
You may need to check your internal grounds, including all screws and any copper fingers attached to boards. As well, the board cage covers need to be attached with all screws, snug but not over tightened. But first add the ground strap to the high pass filter module as shown in the attached photo. This will help with stability. Also check the predriver gain adjustment pot. In a healthy TR7 with the ALC adjustment set for 150 Watts on 20 Meters you should get close to 100 Watts on 10 and 15. This is normal. The ALC and predriver gain adjustments work together and if mis-adjusted can cause issues. You may also want to test the PIN diodes. Procedures are posted on the internet and in this group. On Mon, 03 Feb 2025 08:53:27 -0800 "Michael Jensen via groups.io" <kavigal@...> wrote: Hardly been using it for TX until recently, then I notice that on 10 Meter output is close to 2.5 watts..
Okay, not much.. On 15 meters the current draw is close to 31 amps to produce 100watts! Quite a bit.
more reasonably 21-22 amps on other bands.
So went for an TX alignment, if I crank up the pre drive I can get it up to ~60 watts on 10 meter
obviously not a good scenario and the dr7 board definitely does not like it as the display starts to be all over the place during TX,
with pre drive fully cranked up 40 Meters the PA self oscillates, not good.
So my thoughts, something in the pre drive section or bandpass maybe?
Looking for any suggestions before going nuts down that route.
Thanks on advance!
Best Regards, Michael - oz8abr -- 73 -Jim NU0C
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Re: The mysteriously modified 7077 (and nothing else¡)
That seems likely to be the same cartridge shown in the photos I posted to the group photos section. And yes, as I mentioned previously, it is a cheap CB-era low impedance dynamic cartridge. Thus the need for the transformer to step up the voltage. On Mon, 03 Feb 2025 21:09:56 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: I have just about run to the end of my patience with apps and webpages that still think they¡¯re in 1993.
I should be able to up load photos. I will try again.
Steve Wedge, W1ES
-- 73 -Jim NU0C
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That's what the transformer is for. Although I will say it again, it is not impedance matching. It is a voltage step-up. Impedance matching in microphone circuits is a myth. This is well documented on the internet. Impedance matching is only important when you are transferring power. In fact the pro audio world recommends that the load impedance be 10x the microphone impedance. On Mon, 03 Feb 2025 16:47:04 +0000 "Steve Wedge, W1ES/4 via groups.io" <w1es@...> wrote: One thing of note that I will repeat here is that the element itself -- disconnected from the rest of the mic -- measures 430 ohms with my Fluke 77 in resistance mode. That seems odd if the thing is supposed to be high-impedance. -- 73 -Jim NU0C
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Re: R4B and T4XC Compatble?
Yes, you will need to adjust C61 on the R-4B, exactly the same as if you were using a T-4XB.?
You won¡¯t use the CAR OSC cable and should put a shorting plug in the T-4XC¡¯s PTO LAMP connector.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Feb 3, 2025 at 13:46, C Solomon < cdsol@...> wrote:
Will a R4B and a T4XC transceive?? Is there any difference in the interconnections from if I were using R4B with T4XB?
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Thanks and '73
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Carl - W5SU
Dallas TX
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Also attached as a .JPG file. ? Paul, W9AC ?
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From: [email protected] <[email protected]> On Behalf Of Paul Christensen via groups.io
Sent: Monday, February 3, 2025 7:07 PM
To: [email protected]
Subject: Re: [DRAKE-RADIO] 7077 Mic? Attached below is an LTSpice simulation of Astatic's T-UG8 2-transistor preamp.? Input Z varies between 100 Hz and 3 kHz.??As expected, the input Z varies based on differing hFE (beta) values.? The 2N2712 has a datasheet beta spec variance between 75 and 250.? The simulation uses a beta of 200.?
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Attached below is an LTSpice simulation of Astatic's T-UG8 2-transistor preamp.? Input Z varies between 100 Hz and 3 kHz.??As expected, the input Z varies based on differing hFE (beta) values.? The 2N2712 has a datasheet beta spec variance between 75 and 250.? The simulation uses a beta of 200.?
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Paul, W9AC
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AC-4 Power Supply 10K Bias Trimmer Replacement
I purchased an AC-4 power supply and noticed one of the 3 lugs was snapped off.
Lots of 10Ks out there, but not with two mounting fins for the case.
?
Has anyone replaced these and found a suitable replacement?
?
Many thanks! 73.
--
Joe - W7BWA
Custer, WA
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Jim Shorney
Paul Christensen
